London. 2012.

Banners slung along the outside of the British Museum announce a unique exhibit. The sun shone down, uncharacteristically bright for the time of year, on a throng of unprecedented foot traffic, never mind the weekday cars and lories that kept the streets at a near log jam. Getting to the museum was tricky task for the hundreds coming for opening day, no matter their method.

Except for some.

A man stood beside a lamp post along the road. Next to both was an old-fashioned, large blue police box. No one really payed it too much attention outside the Museum. Why shouldn't it be there, a historic piece of Britannica?

The man beside it tapped a rolled up program against his leg, impatient. "Come on," he said. "We'll miss it!"

"How can we miss it?" The answer came from inside the police box. The door was open just a crack. "We can just pop back in and come back yesterday."

"Timelines, Donna. Timelines. I can't —"

"I know."

Donna stepped out from the blue box, looking absolutely stunning in a 1890s traveling suit done up in sleek gunmetal gray and cobalt blue. She had her red hair piled up on top of her head, held in place by an array of silver pins and one teeny black hat. She made a prim turn round in her costume, before she dropped her artful pose to give him a steely look.

"Doctor, I thought you said we were going to meet Sir Arthur Conan Doyle. Before he was made a 'Sir', anyways." She gestured at the modern London all about them. "We are very much post-Sir."

The Doctor looked her up and down appraisingly, and with approval, then offered her his arm. She took it, rolling her eyes.

"Yes, well, we were," he said. "Old girl's being twitchy. Brought us here instead. Next best thing, I suppose."

"Not really. I dressed up for the occasion. Unlike you, in your brown suit that you wear everywhere but no one ever seems to notice, I'm in a bustle!" They ascended the steps, then whined. "A museum? All of time and space and you bring me on a school outing."

"Behave, or you'll go straight to study hall."

The pair joined the eager public and entered the Museum. The Doctor flashed his psychic paper, and they were admitted without purchasing tickets. The Doctor's face lit up like a school boy's when he took in the Arthur Conan Doyle exhibit, which had taken over a good quarter of the museum's main floor. Even Donna's ruffled air softened. The pair flit from display case to display case of costumes (both real and from various adaptations), manuscript originals, to even mock-up of the apartment on Baker Street side-by-side Doyle's own study. They ended up criss-crossing the exhibit several times, as the Doctor didn't seem capable of focusing on one thing for very long. But each time they got closer to one particular piece of the exhibit: an ornate clock done up in two metals, silver and gold, but the hands frozen in place.

When the Doctor passed it a fourth time, he scrunched up his face. "Hold on." He changed direction abruptly, even for him, and knelt down beside the low table.

Donna, meanwhile, not expecting that much of a change in direction, nearly toppled. She righted herself with affronted aplomb and a hissed warning: "Bustle!"

He ignored her, taken with the display piece. He pulled his pair of glasses out of his suit pocket, still squinting. "Doesn't look right."

Donna followed suit, squinting at the clock. "It's a clock. How does it look wrong for a clock? All right, it does look a bit odd." Then she glanced down at the display table. "Hmm. There's no plaque."

"It doesn't fit. In all the stories, never once was a clock important in any way. What's it doing here?" He scanned the exhibit and its visitors. Everyone seemed to be avoiding the clock, giving the display a wide berth all without looking in its direction.

"Does it even work?" she asked. "Look, the hands aren't moving."

Donna went to touch the clock, but the Doctor swatted her hands away. She rolled her eyes, mouthing, Fine. Satisfied, he furrowed his brows even deeper in concentration, and reached out and touched the clock himself.

The hands of the clock ticked forward with a strike of sound so loud that they both winced. The other visitors to the exhibit first began to slow down and then they stopped altogether, frozen in motion like a photograph behind bent glass. The Doctor and Donna huddled by the table, then noticed as the hands of the clock start to spin like a child's top.

The Doctor quickly pulled his hands away, his face twisted in horror. The arms of the clock slow to a normal pace, one second at a time, but the bubble around them, twisting the world like a funhouse mirror, stayed in place.

Donna said, mildly, "Oh, that's not good, is it?"

"Not. Good. At. All."

Dr. Watson turned over the oxygenator in his hands in the hallway. The brass had been shined, but there were deep scores in the metal — it had taken a great deal of abuse. But had survived. He headed back to the study. Perhaps there was something on the box that might give him a clue as to the box's origins.

As if he didn't already suspect.

Gladstone huff-huffed into the hallway on his stubby legs, looking terribly pleased about something.

Watson was halfway into the study when the door behind him closed. And not by his hand. Watson's first impulse was to tense up, ready to defend against an attacker. He even had his hand curled around the oxygenator to use it as an impromptu brass knuckle, but the sight of Holmes wearing another pair of his ridiculous disguise-pajamas stopped him with a wry grin.

Watson set the oxygenator down on his desk. "Were you disguised as my chair the entire time? That was you?"

Holmes swept his arms theatrically wide, grinning like the madman he was. "In the upholstery."

Watson didn't let him finish his bragging. He clasped his old friend hard, and Holmes reciprocated.

"You damned fool. We all thought you were dead!"

"And so I shall remain for a time."

Watson pushed him away. "What?"

From the two rooms away, Mary's voice called up, "Well, did you find anything more, dear? No idea where the package came from?"

Holmes seized Watson tight by the arm. "Mary mustn't know of me!"

"That's preposterous. She's my wife, Holmes."

"No one is to know. Mycroft's orders!"

"What, you saw Mycroft before me?"

"No. But —"

High-heeled footsteps, first clacking on hardwood floors, then carpet-muffled, came closer. "Husband?"

Holmes gave Watson the eye. "National Security."

Watson knew he wasn't going to win this argument, and wasn't too keen about explaining disguise-pajamas. Or if he could. "Oh, for God's sakes. Where are we going to put you?"

Sherlock scanned the room and started to talk so fast that the words all ran together. "We're on the third floor and you have no balcony, a choice I would normally applaud as a sound security measure but inconvenient now. There is no other exit from this room, and no closets. Unless you've had a secret passage installed since you bought the place —"

Watson pushed Holmes back into the chair. "Don't. Move."

Holmes took position just as soon as he landed. Now a disembodied Sherlock Holmes head hovered above the 'empty' chair. No time for the madman's mask, Watson thought. He yanked his coat off the rack and threw it messily over Holmes's head.

Just as Mary opened the door and entered.

"Well?" she said. "Did you find anything?"

Watson held his tongue, waiting to see if his wife would find anything amiss. Holmes sat statue-still in the chair.

"No," Watson finally said. "Someone's idea of a joke, I'm afraid." He walked back over to his desk, picking up both the package and the oxygenator.

"A poor joke. But I suppose, considering Holmes, it is to be expected."

And while Watson could hear the strange affection for his old friend in her voice, the chair behind her seized violently. Mary was just about to turn her head, when Watson coughed loudly and said, "I think I'll bring them to his flat."

Mary gave him that look. "You must decide what you're going to do with Baker Street estate. Mycroft should be looking after it, not you."

"But Holmes left it to me," he said with a sigh. "I'll never be free of him. I should just sell the lot." This he directed at the chair.

The chair remained still. Almost.

"Well, then take Gladstone with you, so Mrs. Hudson doesn't have to bother stepping out." Mary turned suddenly and reached for the jacket. Watson froze where he stood, waiting for Mary to start screaming, but she grabbed the jacket and turned round just as fast, offering it up for him to pull on. Holmes, exposed behind her, made a horrified face.

"Do ask her again to come stay with us." She slid the jacket onto his shoulders, patting it down. "She shouldn't be in that awful place all alone."

Awful, the disembodied Holmes mouthed in protest.

"Quite right, dear wife." Watson turned and swept her into his arms and landed a kiss on her cheek. "Back soon."

She kissed him back, and winked, as though she didn't believe him for a second. "Don't forget to be back for the train to Brighton."

After she left the room, Watson let out a grand sigh, and took in the sight of his partner. "We need to get you into something else."

"Awful?"

Watson rolled his eyes. He pulled on his bowler. "Come on, Holmes."

"I need a machete to get through." Watson pushed his way through the hellishly verdant canopy of tropical ferns and flowers. "How does it all even manage to grow? There's not enough light in here for an African Violet."

"Ah," Holmes said. "But the vegetation of the tropical regionsis so dense, their canopies so full, that only those most sensitive to the smallest amounts of light can —"

"Do shut up, Holmes."

They had made it to the heart of the cultivated jungle, Holmes's study. It was as they had left it: overgrown and in disarray, all save for a tortoiseshell table in the center of the room, cleared off of papers, cigarette ash and dust. On it sat a single envelope pressed with a red wax seal.

"Would you really sell it all?" Holmes almost sounded hurt. And, Watson thought, looked faintly ridiculous, wearing an oversized coat and top hat that Mary's brother had left behind after a night of cigars, brandy and poor wagering (on his part, not Watson's). But it was all they could manage with what they had.

"Don't play daft," was Watson's reply. "You're not good at it." Watson eyed the letter, tapping first it, then the table, with the end of his cane.

Holmes looked measurably relieved. He dropped the great coat on the floor and knelt down beside the disturbance — the letter.

Watson walked to the window, pulled back the curtain, and peered out into the street.

"So, Mycroft knows you're here but you haven't seen him yet."

The street below appeared normal, quiet. He watched Mrs. Hudson, Gladstone trailing behind, hail a cab. She'd been quite amenable to taking Gladstone and visiting her sister for the following week, perhaps relieved to not worry about the flat and its unmanageable contents. Especially now. Watson was already trying to think of something he could tell Mary. Brighten would once more be put off. Perhaps he could blame a patient in dire condition, needing immediate care?

"No," Holmes said. He licked the table's edge, then picked up the envelope and did the same. "I sent him a telegram, encoded three times, before crossing the border. This is from him." He offered up the letter and indicated the seal.

Watson sighed. Patient in dire condition, indeed. How many honeymoons would the man ruin?

"Why are we doing this?" he asked sharply. "Hiding you? Don't you think the world could use its only Consulting Detective for actual detecting?" Watson, satisfied they had not been followed and that Mrs. Hudson was safely away, let the curtain fall.

"I will be better able to do so, at least for the time being, anonymously. And Mycroft agrees." He stood up abruptly from the floor, letter in hand, and took a letter opener from the bureau. "An invitation."

"An invitation to what?"

"To a mystery!"

And so, the Hound of the Baskervilles, or, John thought to himself, the H.O.U.N.D. Project, was safely behind them. The moment they'd finished lunch at the vegetarian pub, Sherlock had tossed John the keys to the Jeep and slunk into the passenger side with his collar turned up and his eye to the window. Switching off at Paddington, they traveled on by train in silence, but not, John noticed with some alarm, the usual kind. John kept stealing looks at his friend. And every so often, John caught Sherlock stealing a look back. As the sun slid down first behind the Moor and then behind the growing urban landscape toward London, the silence between them stretched out longer than it ever had.

John had gotten used to those silences — treasured them impishly when Sherlock had been a total shit, worried over them when Sherlock had gotten into one of his moods of the sort that Mycroft would warn John about.

But this silence was different.

John kept as quiet as Sherlock, afraid to break the spell. By the time they'd gotten home, John wished he knew how.

It was late when they pulled to the station, later still when they were dropped off by cab outside 221B. The rain they had avoided on the Moors had manifested fully on London, turning the streets shiny black and drowning out the sounds of vehicles and scarce foot traffic. John's heart sank when he realized Speedy's was already closed. No warm meal tonight.

"Anything in the fridge besides toes? I'm half-starved. Do you want to see if the Italian place is still open?"

But Sherlock was already inside, the door to 221B open into darkness.

"Never mind, then." John sighed and shuffled in behind, wet as a cat and about as impressed. John juggled now unnecessary keys and bulky suitcase and got inside.

Sherlock had left the light off in the entrance, and upstairs. Not a light on at all, John thought crossly. He banged his knee taking the corner, dropped the suitcase, then dropped his keys. "Fuck. Sherlock…" he said, scrambling to pick up both.

A single bright light came on in the study, a spotlight on the desk with Sherlock's silhouette standing just off to the side. Under the harsh light lay an envelope.

His annoyance temporarily forgotten, John asked, "Do we have mail?"

"No," Sherlock said.

"What is it, then? Who's it from?"

Sherlock said nothing for a long time. More silence, then he ran his finger along the edge of the envelope.

"Sherlock?"

"It can wait until morning." Sherlock yanked the chain of the desk lamp, and the study plunged into darkness.

John woke to the smell of coffee.

Which was impossible. John squinted, pulling the sheets up higher over his head. But, no, coffee. Clearly, he thought with some degree of alarm, that was the smell of coffee. He bolted upright, body ready to fly out of the bed and deal with the obvious intruder in the flat and fearing for Sherlock.

Who was standing above the bed, cup of coffee outstretched over John.

John nearly fell off on the other side of the bed.

"Jesus Christ!" He twisted the sheets around him protectively. "What are you doing in my room?"

Sherlock furrowed his brow irritatedly. "Coffee," he said. He wiggled the mug.

John sighed and took the cup. He sat up properly in bed, resigned to the intrusion. That was when John noticed his closet was open.

"Looking for a jumper?"

Sherlock snorted as he crossed the room over to the closet. "I have to make sure you have something appropriate to wear."

"For what?"

"For the gala." Sherlock picked through closet.

"Gala what?"

Sherlock made an exaggerated sigh. "The letter, the invitation," he said, as if it was all old news now, boring. Sherlock tugged out one V-necked cardigan and made a face. He motioned behind him to the edge of the bed, where the envelope from last night had been casually tossed.

"I think I've missed some steps," John said. "And there's nothing wrong with that cardigan." He reached for the letter, making sure not to lose what little of the covers he had. Sure enough, two invitations as well as a hand-written letter from Mycroft that read: A request from a friend that I cannot deny. He expects trouble and he needs you to guard the timepiece.

John flipped the tickets over, and back again. "Was this what was on the table downstairs?"

"Good, John." Sherlock had paused over a dark suit hidden in the back of the closet, so John couldn't tell if he meant the suit or John's deduction.

John returned to the tickets. Tickets for two, to a special exhibit at the Museum of London. "What is this now?"

"We're going out tonight." Sherlock returned to the side of the bed, John's suit in hand. He laid it atop the other half of the bed.

"Two tickets. Stag again, eh?" John winced at how awkward that sounded. And he was feeling even more uncomfortable, naked save for his bedsheets, by the minute.

Sherlock said off-handedly, "We leave in an hour."

"We're body guards for, what, a clock now?" John chuckled, but Sherlock remained impassive. "Wait, in an hour?"

"It's nearly four. And I want to get a good look 'round before it starts." He was already dressed in his finest, the black suit with the burgundy shirt.

"Why the hell did you let me sleep so long?"

The smallest of smiles quirked Sherlock's lips before he walked out of John's bedroom. "Hurry up, then," he called over his shoulder.

"I have never seen you in anything more ridiculous. And I've seen you in a dress, now, God help me."

"Which is why it's perfect. Don't you trust me, Watson?"

"You look like Father Christmas." Which was terribly charitable, if Watson was truthful. Holmes had cobbled together a disguise from the bits and bobs of his disguise closet, and now looked like someone else besides the recently deceased Sherlock Holmes. Dressed in a Highland frock coat stuffed with a down-filled fake belly and topped off a frilly white beard that came halfway down his chest, Holmes doddered about on a silver-handled cane like one of the old gentry trotted out to make social appearances. He was completely in character; in fact, he had abandoned Watson and made his way over to a clutch of society ladies.

At least, Watson thought with some relief, what he wore couldn't be called pajamas any longer. Or the 'urban camouflage' he insisted on calling it. Watson had long ago started being thankful for the small miracles of his life. If he hadn't, Holmes would have driven him mad years ago.

Watson grabbed a glass of wine from a man with a passing tray, and watched his old friend as he did his work. Holmes, as the genial and moneyed old Mr. Freeman, a persona Holmes had cooked up years go that he'd taken to great lengths to age purposely, salaciously flirted in character. The three society women trilled in hysterical fits of nervous, but appreciative laughter. And from laughter would come gossip, the kind that Holmes was on the hunt for.

Watson's role, as usual, was to get close to the object of their investigation.

The British Museum sparkled with gaslights just as brightly as it sparkled with wine and conversation. Men dressed in their finest suits, women in elegant formal wear, all of them delighting in the opportunity to see and be seen. These sorts of events always set Watson's teeth grinding — at least until he'd had a few glasses himself. But he'd have to hold back tonight thank's to Mycroft. However, Watson wasn't entirely sure Holmes should so quickly be on the heels of another case, especially after Moriarty. Not that he'd be able to shake his old friend off the hunt now.

Watson cut a slow, winding path through the reception, stopping to chat amiably but briefly with those he knew, introducing himself to those he didn't. All the while he kept his eyes on the crowd. There were five men dressed in identical suits, all of them in full beards. They did not mingle with the other guests and their near identical manner kept Watson's attention prickling.

But at last Watson made it to the center of the reception — a solitary dais holding up an ornate gold clock. It was an airy creation, looking as though half of it had been pulled out by a mad designer. Yet the hands ticked softly, despite what might be missing.

"It appears so uninspiring, doesn't it?"

Watson looked up. 'Mr. Freeman' stood opposite. Watson pitched his voice low. "It does look like just a clock, however well-crafted. What's so special about it?"

"Someone wants it." Holmes pulled down the tiny spectacles that were part of the disguise and leaned in for a closer look. "That's all it takes, really."

"Surely if they wanted, someone could buy it or have one made for them."

"Of that I'm not so sure." Holmes took off the fake spectacles. "It is ingeniously designed."

"Yes, it looks like it shouldn't work at all. Quite artful." Watson, not one for design, kept his eye on their fellow attendees to make sure their collective attention was not on the pair of them. Indeed, it looked like the party would go on for hours, clock or no clock. However, the five men in their jackets and beards, started to move against the jovial and disinterested tide of the guests.

"No, not art," Holmes said, clearly pleased. "There is no reason why it should work at all. It quite literally missing half its constituent parts."

Watson frowned. "That's impossible."

Holmes looked up at Watson with a wide grin. "Wonderful, isn't it?" Holmes bent down to the clock, and removed his white gloves.

Watson, dropping the pretense of indifference, watched the five men boldly. There was no mistaking the pattern now. They were heading for the dais, and the clock. Would-be thieves, or hired guards? Either way, they would intervene. "Holmes."

"And the mechanisms are unlike anything I've ever seen. Even the most advanced theoretical models can't explain how —"

"Holmes!" Watson moved around the side of the display, jostling Holmes. The men closed in, reaching into their breast pockets and pulling out — "Guns. Holmes, they're armed."

But Holmes paid him no attention. Instead, he lifted his hands and reached out to touch the clock.

"A moment, Watson. I just have to see how this works …"

John followed behind Sherlock, pulling the too-tight suit jacket down again. Sherlock swept through the security lines in that confident manner that John hadn't gotten used to and probably never would. Not that anyone could own the British Museum, but it certainly wasn't for the public today, and their tickets gave them no-questions-asked access.

"Mycroft is taking this threat seriously," he said to Sherlock. He then flashed an apologetic smile at the guard as they made their way past.

"He wouldn't have asked us to come otherwise."

Now that they were behind enemy lines, Sherlock switched 'on' in that mechanical way of his, eyes narrowing as he scanned the room. Who knew what Sherlock saw, but John was able to pick out the hidden security working the event for the Museum as well as the regular blokes in uniform. The undercover ones were all burly fellows to a man, and armed by the looks of the bulge in their right breast pockets.

It was a circular room, with a dais in the center. Other displays had been cleared away to make room for the guests. John and Sherlock stayed unobtrusively to the sidelines as the glitterati mingled and drank, laughing too loudly at their own jokes and congealing into even larger social circles. John wondered how many of them had set foot in the Museum, or any museum for that matter, before today.

The more John thought about it, the more it bothered him. "Odd place for a non-historic display, isn't it?"

Sherlock barely nodded, instead taking up position in one darker section of the room. John followed, picking up a drink as it went past on a silver tray. He tried to make eye contact with the waitress, a stunner with long legs and hair pulled back into a severe black queue, but she walked on past, face like a statue.

Sherlock glanced at John sidelong, snorted. "Married. And gay. Try again, John."

John looked down into the contents of the glass, then drained it. "All right then, what else do you see, besides my utter lack of prospects?"

"No prospects at all, for either of us I'm afraid. There's no mystery here, no puzzle." Sherlock leaned against the wall, and folded his arms. "And there is more than enough security here." He motioned to the men John had noticed earlier.

"What about the gizmo?"

"A clock," Sherlock said. "Who cares?"

"Well, Mycroft certainly cares. Not that you normally care when Mycroft cares. Why are you doing him this favor, anyways?"

"It was either this or be brought up on charges for that breach of security up in Baskerville."

That amused John immensely. "Blackmail. Very good." John found a place for his empty glass. "Let's see what this clock is all about."

John headed down into the throng, mingling ably enough until he was at the dais itself. Sure enough, not a damn one of the guests had paid it any attention. Not that they would have profited from that attention, had they been so inclined. There wasn't a card or plaque or anything by the device, but the clock was striking enough not the need any description. Silver, or possibly platinum, it was ornately made, metal twisted into whimsical shapes. Yet it looked like half of it had been sheered off, like one of those science experiments when you cut away half the object to show how it really works inside. Except this didn't illuminate anything. With half its gears missing, it still worked; the hands ticked sedately along as if nothing was the matter.

Sherlock had pulled up alongside him, eyes on the clock.

"Oh, you're interested now?"

Sherlock knelt down. "It's the only interesting thing left in the room."

John ignored the slight, and grabbed another drink as it whizzed by, this time in the hands of a blonde.

"Jailbait," Sherlock said tiredly.

"I wasn't looking."

"Were."

"Wasn't." John downed the second drink, remembering only afterwards that he was drinking on an empty stomach. As he pondered this, one of the big burly fellows started to make his way towards the dais, and the pair of them.

"Um, Sherlock. Mycroft told them we were coming, right? We're expected. Right?"

"Not so boring after all," Sherlock said, still focused on the clock and the words coming out almost like a purr.

Uh-oh. John knew that sound. Something had gotten Sherlock's attention, and it wasn't the one guard - no, two guards now, heading over to them. And reaching into their jackets.

"Um, Sherlock?" A third left his post and was heading their way.

"This clock is running on no perceivable power source." Sherlock's voice started to rise. He flexed his fingers. "It's defying at least two laws of physics at this precise moment. Exquisite. John, take a closer look."

"I think those men are coming to have a closer look at us. Seriously. I don't think these guys are on the same side as we are —"

The first man was now only two strides away. His lips curled back into a grimace but only steel flashed beneath. John dropped his glass. The second one loomed up on the other side. Underneath his dark sunglasses came the strangest light.

"Sherlock!" John jabbed him in the shoulder. "Company. Incoming!"

"One second, John. One ... second …"

Sherlock flexed his fingers, and lay them on either side of the clock.

Two sets of hands touch the same clock.

Light flares from a single point where both both clocks, both men, impossibly exist in the same point in time and space. In unison, they wince, hands reflexively letting go of the device.

Concussion. Ears ring, vision doubles, stumbles backwards.

Behind them, a man shouts a name.

A distraction. They refocus their sights on the device, unable to look elsewhere. The arms of the clock continue to tick on with a sound that drowns out all the shouting and everything else. They reach out for the clock.

But there is another man where there was not one before. He stands behind the dais wearing a stranger's face, but in the span of the tick of another passed second, he wears a face each man knows: Moriarty.

He flashes a triumphantly cold smile that Sherlock Holmes will know until his very last breath.

And while the room fractures into light, as glass shatters and men and women recoil from the force of the blast, Moriarty stands untouched in the center of the chaos. He leers, just before his faces changes back to that other unknown face, and back again, like two photograph negatives superimposed.

"Tut, tut," he says, the only sound that Sherlock Holmes can hear above the sound of that damnable clock. "Can't have you helping the good Doctor now, can we?"

Light drives in to all the cracks of the world.

Sherlock Holmes shields his eyes . . .